PTL 1 discloses an X-ray generating tube including an insulating tube, a cathode, an anode, and an inner anode layer. The insulating tube, the cathode, and the anode constitute an envelope that defines an inner space, and the inner anode layer extends from the anode along the inner surface of the insulating tube. The inner anode layer is electrically connected to the anode and suppresses charge of the insulating tube.